1. Field of the Invention
This invention relates to foam integrated innerspring mattresses and, in particular, to a method of manufacturing foam integrated innerspring mattresses wherein a flexible polyurethane foam is adhered onto the top and bottom of individually wrapped pocket innersprings, and additional polyurethane foam is molded onto the sides of the mattress. As used herein, the term “foam integrated innerspring mattress” is intended to be construed in its broadest sense. In general, a mattress is designed to provide support for a person sleeping thereon.
2. Reference to Related Art
Innerspring units formed of a unitary construction are known. For example, in U.S. Pat. No. 3,239,584 issued to Terry et al. on Mar. 8, 1966, a method of fabricating a seat or cushion using a combination construction of springs and resilient pads is shown. A spring wire element with an open mesh fabric placed thereon is used and a resilient foam is foamed through the open mesh fabric to bond the spring wire element, the open mesh fabric and the foam into a unitary structure. The structure is used primarily to manufacture seats for vehicles.
In U.S. Pat. No. 3,920,609 issued to Lehmann on Nov. 18, 1975, a method of producing a spring core mattress using coil springs that are at least partially embedded in cover plates is shown. The cover plates are positioned so as to be substantially parallel to each other while the coil springs are under a preload and are surrounded by foam material to hold them in their respective relative positions, The foam material is provided as foam sheets and is not foamed directly onto the cover plates.
U.S. Pat. No. 3,325,834 issued to Lovett et al on Jun. 20, 1967 shows a method of making an innerspring body supporting article. The innersprings are embedded in adhering particles of multi-cellular resilient spongy material in order to provide a sturdy long-lasting resilient unitary structure. The particles of resilient spongy material are coated with an adhesive prior to being deposited and pressed into a mold. The innerspring structure is completely covered with the coated particles and a unitary structure is formed when the adhesive sets. A divisional application of this patent issued as U.S. Pat. No. 3,452,127 on Jun. 24, 1969.
Other spring reinforced mattresses wherein a foam or other type of resilient material completely surrounds an innerspring are shown, for example, in U.S. Pat. No. 2,994,890 issued to Wagner on Aug. 8, 1961; U.S. Pat. No. 3,099,021 issued to Wetzler on Jul. 30, 1963; and U.S. Pat. No. 3,049,730 issued to Wall et al on Aug. 21, 1962. Wall et al specifically relates to a seat structure wherein a first layer of polyurethane foam is used to embed a spring. A second layer of a less dense polyurethane foam is provided on top of the first layer of foam in order to provide increased comfort.
U.S. Pat. No. 4,811,439 issued to Siegel on Mar. 14, 1989 discloses a method for producing a foamed innerspring unit comprising the steps of preparing a foamable reaction mixture, spraying it into a tray, loading an innerspring unit into it and permitting the foamable reaction mixture to rise to form a foam that is at least partially adhered to the unit.
U.S. Pat. No. 5,756,022 issued to Siegel on May 26, 1998 disclosed a method for forming a foamed innerspring unit including releasably securing a plurality of coils to a jig, delivering a foamable reaction mixture to a tray and positioning the jig so that the ends of the coils extending away from the jig are spaced from the bottom of the tray so that the rising foam embeds the end of the coil. The process is repeated by releasing the foamed layer embedding one end of the coils, releasably holding the first foam layer with the ends thereof spaced from a tray having said foamable reaction mixture therein so that the second end of the coils is embedded in a second foam layer.